The present invention relates to self-expanding, knitted devices and more particularly, to a self-expanding knitted device for intravascular repair of distal and tortuous vasculature.
The vasculature of an animal or a human characteristically suffers from a variety of maladies. Vessel walls can weaken and become distended over time in response to blood flow and pressures, thereby resulting in formation of aneurysms. Such aneurysms can take on a myriad of forms. In particular, aneurysms may form at or near bifurcated vessels creating enlarged areas about the bifurcation, or may form a pocket, for example, in side walls of vessels. Due to the complications associated with aneurysms that rupture or otherwise fail, it is critical that an aneurysm be treated expeditiously and effectively. Intravascular treatment procedures include placing grafts within the aneurysm in a manner to ensure that blood flows through the graft rather than through the weakened vessel. Additionally, in the event that the aneurysm is in the form of a pocket in the side wall of a vessel, a stent might first be placed at the repair site then the pocket filled with material such as coils.
Stenoses also typically form in vasculature of humans and animals. Specifically, thrombotic or atherotic stenoses can form nearly anywhere in the vasculature. Such narrowing of the vessel is, of course, highly dangerous to the patient where the afflicted vessel provides the sole blood flow access to critical parts of the body. To treat such stenoses, a supporting structure can be placed at the diseased site for the purpose of enlarging and holding open the vessel. It is known in the art to employ stents for this purpose.
Vessel occlusions can also be treated by employing devices which are actuated to debulk and remove vessel occluding thrombi. This procedure is generally referred to as a thrombectomy. Typically, such devices are intravascularly advanced to the repair site and manipulated to remove the unwanted material from the vessel by physically engaging the thrombus and severing the same from the vessel wall.
Due to procedures such as thrombectomies or due to the natural, albeit undesirable, function of a patient""s vasculature, emboli may be found traveling through a blood vessel. Embolic material can cause unwanted blockages or otherwise facilitate the formation of an occlusion in a vessel which too, can be highly dangerous to a patient. To address this problem, emboli-catching filters can be intravascularly placed within vasculature to thereby provide embolic protection. Such devices are often implanted temporarily within vasculature and removed upon being satisfied that the undesirable embolic material has been captured.
In certain situations, it is desirable to aid the formation of thrombus. For example, devices may be placed within aneurysmal spaces to slow and eventually cease blood flow therethrough. This procedure is sometimes referred to as embolic therapy, the basic thrust of which is to minimize or eliminate exposure of weakened sections of vasculature to blood flow and pressure.
Unfortunately, many areas of vasculature are inaccessible by a conventional intravascular repair means because the repair devices typically employed are often too large or rigid to be effectively advanced through tortuous vasculature or to vasculature that is very distal to the site through which the vasculature is accessed. Alternatively, in the event that there is success in advancing the repair devices to the diseased portion or repair site of the vasculature, conventional repair devices sometimes lack a large enough expansion ratio and/or radial stiffness to accomplish the necessary repair. Moreover, conventional devices can lack a profile suited to avoid traumatic engagement with a vessel wall or sufficient radiopacity so that remote observation is impossible.
Thus, where an intravascular approach is not available to the physician, invasive surgical techniques must be applied. To wit, a patient""s chest, abdomen or cranium, for example, must be directly traversed in a major surgical procedure.
Hence, those concerned with repair of diseased vasculature have recognized the need for devices that can be employed to effectively repair distal and highly tortuous vasculature. The present invention fulfills these needs.
Briefly, and in general terms, the present invention provides devices contemplated for the repair of highly tortuous and distal vasculature. Basically, the invention is directed to a self-expanding, pseudo-braided structure that is characterized by having a large expansion ratio and high flexibility as well as an improved radial strength accomplished through the advantageous utilization of deflection energy.
In one preferred embodiment, the devices of the present invention are fabricated from a single filament configured into a repeating helical pattern that is interlaced into a mesh or pseudo-braided tubular shape. The filament may embody an elongate highly elastic and shape settable material. A reversal of direction that the filament undergoes presents a blunt, rounded surface that is atraumatic to vessel walls. The structure in the present application is referred to as pseudo-braided. Braiding is the interlacing of at least three wires at various angles to each other to form a braid, whereas the present invention uses a single filament that is interlaced with itself along the length of the structure at various angles. It is within the scope of the invention to interlace another filament or a plurality of other filaments into the pseudo-braid formed by the single filament.
In another aspect of the invention, the pseudo-braided or interlaced structure has a high expansion ratio with a low metal to space ratio. A large expansion ratio is accomplished by the unique single filament construction that provides additional springback forces.
In other aspects of the invention, there are various methods for terminating the filaments. Additionally, various methods are contemplated for adjusting the radiopacity as well as the expansion and spring characteristics of the pseudo-braided devices. Various methods are also contemplated for improving coverage of the pseudo-braided devices and enhancing the anchoring of the same within distal and tortuous vasculature.
The self-expanding, pseudo-braided devices disclosed are intended for use in addressing various maladies effecting vasculature. In particular, the self-expanding, pseudo-braided devices can be configured specifically to facilitate the repair of aneurysms and stenoses as well as to act as filter or thrombectomy devices.
These and other objects and advantages of the invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings of illustrative embodiments.